Interpretive Summary: The redbay ambrosia beetle (RAB) is an exotic wood-boring pest that transmits laurel wilt, a deadly fungal disease that threatens the avocado industry in Florida. Development of effective lures for detection and control of RAB will require a better understanding of the host-seeking behaviors of this new invasive pest. Scientists at the USDA-ARS in Miami, FL conducted a comparative study of flight behaviors in RAB and two closely-related ambrosia beetles. They discovered that female RAB fly several hours earlier than the non-pest ambrosia beetles, providing a perfect window for selective capture of RAB and potentially for selective pest control. The scientists also developed an electrophysiology method to measure olfactory response of ambrosia beetles to odors from host wood and from essential oil lures. Future research will use this method to identify the specific chemical attractants used by RAB for location of host trees. This information will be used by ARS scientists to develop improved lures for early detection of RAB and also for development of prototype attract-and-kill (bait station) systems to reduce spread of RAB in commercial avocado groves.

Technical Abstract:
The redbay ambrosia beetle, Xyleborus glabratus Eichhoff, is an exotic wood-boring insect that vectors the mycopathogen responsible for laurel wilt, a lethal vascular disease of trees in the Lauraceae, including avocado (Persea americana Mill.). Effective semiochemical-based detection and control programs for X. glabratus will require an understanding of the chemical ecology and host-seeking behaviors of this new invasive pest. This study (1) presents an electroantennography (EAG) method developed for assessment of olfactory responses in ambrosia beetles; (2) uses that new method to quantify EAG responses of X. glabratus, X. affinis, and X. ferrugineus to volatiles from three host-based attractants: manuka oil (essential oil extract from Leptospermum scoparium Forst. & Forst.), phoebe oil (extract from Phoebe porosa Mex.), and wood from silkbay (Persea humilis Nash); and (3) documents temporal differences in host-seeking flight of the sympatric Xyleborus species. Field observations revealed that X. glabratus engages in flight several hours earlier than X. affinis and X. ferrugineus, providing a window for selective capture of the target pest species. In EAG analyses with X. glabratus, antennal response to phoebe oil was equivalent to response to host Persea wood, but EAG response elicited with manuka oil was significantly less. In comparative studies, EAG response of X. glabratus was significantly higher than response of either X. affinis or X. ferrugineus to all three host-based substrates. Future research will use this EAG method to evaluate olfactory responses to synthetic terpenoids, facilitating identification of the specific kairomones used by X. glabratus for host location.